Save the butterflies, keep the milkweed

Wednesday

Jun 18, 2014 at 2:00 AM

I was about to mow recently and was thinking about what to do with two milkweed plants that had pushed their way through some tangled grass behind my chicken coop. That got me thinking about the much larger patch of milkweed coming up in my neighbor's field.

I was about to mow recently and was thinking about what to do with two milkweed plants that had pushed their way through some tangled grass behind my chicken coop. That got me thinking about the much larger patch of milkweed coming up in my neighbor's field.

And both these thoughts made me think about how monarch butterflies all over North America rely on milkweed fields to survive. This has been, and is predicted to be, a very bad year for monarch butterflies all over North America.

Monarch butterfly populations have been in decline for over a decade, and things aren't looking up. A recent study published just last week in the Journal of Animal Ecology picked apart the various factors thought to be leading to the plummeting monarch butterfly population, things like a reduction in their breeding and wintering grounds in Mexico, colder-than-normal winters in the south, a lingering drought in the south.

Scientists previously thought that changing wintering grounds in Mexico, impacted by climate change and deforestation, were the main drivers in the decline of the monarchs, spurring regional legislation to protect their winter habitat. This has undoubtedly helped, but the new study indicates that the primary driver in monarch decline rests in the American Midwest, specifically in the loss of milkweed, the only plant that monarchs lay their eggs on, a plant vital to their survival.

According to Ryan Norris, co-author of the recent report, monarch butterflies are extremely sensitive to changes in the availability of milkweed. Milkweed is the primary food source of larval monarchs, they are the only plants that the butterflies can lay eggs on. Consumption of milkweed by caterpillars is an integral part of the monarch lifecycle. Their primary defense against predation is their color, which to predators indicates that they are poisonous and they taste bitter, an attribute they acquire by eating milkweed as caterpillar.

Throughout the eastern United States, but in particular in our agricultural belt, milkweed is making way for crops. Norris' study indicates that industrial farming has contributed to a 21 percent decline in milkweed plants between 1995 and 2013. Of particular worry is the connection this study makes between genetically modified, herbicide-resistant crops and the current population decline of monarch butterflies. The issue with herbicide-resistant crops is that you can plant your crops, soybeans for example, and then blanket the area with herbicides, killing all the "weeds," weeds like milkweed.

While the big problem appears to be agricultural practices in the Midwest and southern states, we won't have monarchs in the Northeast if we don't tend to our milkweed as well. We can choose to avoid mowing fields where milkweed grows. We can choose organically grown crops. Numerous studies have shown that small farms that plant a diversity of crops, especially farms that use organic, sustainable farming practices, have increased diversity both on their farmlands and in surrounding areas.

One might argue that monarch butterflies are a tenuous species, relying upon a fragile network of unlikely coincidences; perfect conditions at every stage of their migration, perfect weather in the south, perfect timing so that the one plant they need to succeed, milkweed, can flourish. Perhaps they are destined for an early extinction, even without human encroachment on their migratory routes. Or, perhaps, they are perfectly adapted to their world.

I, personally, don't want to be a part of their demise. I'm going to nurture those two milkweed plants near the chicken coop, and am going to try to talk my neighbor into not mowing the part of their field where the milkweed grows, and hope that some monarchs make it north this summer and find a safe haven in my backyard.

Sue Pike, a researcher and an environmental sciences and biology teacher at St. Thomas Aquinas High School, welcomes your ideas for future column topics. She may be reached at spike3116@gmail.com or via her blog, sp.stalux.org.

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